Method and Device for the Cooling of Articles

ABSTRACT

The method and device according to the invention for the cooling of articles, in which the articles are introduced into at least one channel, through which a first stream of a first coolant flows, the channel being cooled by a second stream of a second coolant, is distinguished in that the first stream is fed from a first coolant conveyance unit and the second stream is fed from a second coolant conveyance unit. Advantageously, the second stream of the second coolant is a high-purity coolant stream which comprises, in particular, essentially pure liquid nitrogen. High purity is understood in this context to mean, in particular, that the second stream of the second coolant carries with it no articles or remains of articles or other impurities. The cooling conduit thereby remains clean and does not have to be cleaned in a complicated way.

The subject of the present invention is a method and a device for the cooling of articles, which can be used, in particular, for the at least partial freezing of articles. The preferred field of use of this invention is the freezing of liquid and/or pasty substances, for example in and/or for the food industry.

Device for the cooling and, in particular, freezing of liquids are known from the prior art, for example from U.S. Pat. No. 4,843,840. In this case, the liquid to be frozen is dropped into a stream of nitrogen which moves downwards over an inclined plane in a channel. At the same time, the liquid freezes at least on the outside, and, after leaving this channel, the nitrogen is separated from the frozen particles and subsequently used for cooling the channel.

High hygienic requirements must in this case be met particularly in the cooling or freezing of foods. The devices known from the prior art have the disadvantage that the channel is cooled, for example, on the underside by a stream of nitrogen which contains small particles of the liquids to be frozen. These contaminate the corresponding cooling conduit and may lead even to constrictions or blockages of the cooling conduit. Such constrictions impair the stream of coolant through the cooling conduit, and therefore unequal cooling conditions may occur over the length of the channel. This adversely influences the freezing behaviour, and there are no reproducible freezing results obtained. Moreover, this necessitates a complicated cleaning of the cooling conduit. Since the latter is often not openly accessible in mechanical terms, complicated chemical cleaning is required here. This is time-consuming and cost-intensive.

Proceeding from this, the object on which the invention is based is to propose a method and a device for the cooling of articles, in which longer running times and shorter maintenance times become possible and, in particular, a contamination of the cooling conduit is avoided.

This object is achieved by means of a method and a device having the features of the independent claims, advantageous developments being the subject-matter of the dependent claims.

The method according to the invention for the cooling of articles, in which the articles are introduced into at least one channel, through which a first stream of a first coolant flows, the channel being cooled by a second stream of a second coolant, is distinguished in that the first stream is fed from a first coolant conveyance unit and the second stream is fed from a second coolant conveyance unit.

In particular, the two coolant conveyance units are not connected to one another upstream of the respective delivery to the channel and to the cooling conduit designed for cooling the channel. This means, in particular, that the second stream of the second coolant, after flowing through the cooling conduit, can issue into the first stream of the first coolant, but the first stream of a first coolant which is in contact with the articles to be cooled is not intermixed with the second stream of the second coolant. The result of this is that a contamination of the corresponding cooling conduit cannot occur when the channel is being cooled by the second stream. What is preferably used as the second coolant is liquid nitrogen which comprises less than 0.1% by weight of impurities, such as suspended matter or the like. Pure liquid nitrogen is preferably used. The first coolant preferably comprises nitrogen. Furthermore, this is preferably added as liquid nitrogen and evaporates at least partially when it flows through the channel. Moreover, the first stream may comprise impurities, for example due to residues of the articles to be cooled/frozen. Since the cooling method is often operated in closed circuit, remains of the articles to be cooled or some articles to be cooled, splinters of articles to be cooled or the like are always found in this first coolant, so that this is usually less pure than the second coolant. However, since the channel preferably has, at least in part-regions, an open design, it can be cleaned by means of cost-effective and simple mechanical methods.

According to a preferred refinement of the method according to the invention, the first coolant, after flowing through the channel, is collected in a sump after it has been separated from the articles.

This advantageously allows a reuse or a further use of the first coolant. In particular, the first coolant or the first stream of the first coolant can flow through the channel in closed circuit.

According to a further advantageous refinement of the method according to the invention, the first coolant conveyance unit comprises the sump.

That is to say, the first stream of a first coolant is fed preferably at least partially, in particular completely, from the sump.

According to a further advantageous refinement of the method according to the invention, the second coolant is delivered to the sump after the cooling of the channel.

This leads to a feed of the first stream from the second stream, by means of which evaporation losses of the first stream which occur during the cooling of the articles can be advantageously compensated. With corresponding method management, it is thus possible particularly advantageously that the second stream and the first stream are in each case set such that the second stream, by being delivered into the sump after the cooling of the channel, is exactly sufficient to compensate the evaporation losses of the first stream of the first coolant. In particular, it is advantageous if both coolants are liquid nitrogen.

According to a further advantageous refinement of the method, the direction of the first stream and that of the second stream are essentially opposite to one another.

This brings about particularly high cooling effectiveness, since the articles are cooled in a first direction and the cooling requirement can be covered by the second stream.

According to a further advantageous refinement of the method, the second stream flows beneath the channel.

This makes it possible for the channel to have a very simple configuration, since it can be designed as the top side of a, for example, metallic component, through which the second stream is led.

According to a further advantageous refinement of the method, the second stream of the second coolant is fed into the cooling conduit with a pressure of at most 0.2 bar.

This makes it possible to operate the second stream solely by virtue of this pressure which is usually sufficiently high to ensure that, on the one hand, the second stream can be maintained and, on the other hand, a sufficiently high cooling power is achieved.

According to a further advantageous refinement of the method according to the invention, the second stream of the second coolant is fed into the cooling conduit with a pressure such that the second stream can be maintained.

This makes it possible to operate the second stream, without forming further components, such as, for example, conveying means, which can ensure a second stream.

According to a further aspect of the present invention, a device for the cooling of articles is proposed, which comprises at least one channel which can be connected to a first coolant conveyance unit such that a first stream of a first coolant can flow through the channel. Furthermore, means for introducing the articles into the first stream are formed. The channel has a cooling conduit which can be connected to a second coolant conveyance unit such that a second stream of a second coolant can flow through the cooling conduit.

This makes it possible, in particular, to cause an essentially pure stream of a second coolant, as a second stream for cooling the channel, to flow through the cooling conduit. The first stream of a first coolant is often contaminated by contact with the articles, since fragments, splinters or the articles themselves are entrained in this. Often, too, even insufficient separation of articles and the first stream is impossible, so that contamination of the first stream of a first coolant occurs successively.

According to an advantageous refinement of the device according to the invention, the channel is delimited at least partially by at least one wall, the cooling conduit being formed on a side lying opposite the channel.

In particular, a plurality of channels may have a common cooling conduit. Basically, in this case, the wall may be designed as a metal strip which, at least in part-regions, is bent in wavy manner in cross section and which forms the at least one channel. Preferably, the wall is produced from a material having a thermal conductivity of 15 W/mK (watts per metre and Kelvin) to 25 W/mK, preferably 18 to 22 W/mK.

These thermal conductivities have proved particularly advantageous for implementing an effective cooling of the channel. Preferably, in this case, the wall is produced from a metal.

In particular, at least one of the following components:

-   -   a) the channel     -   b) the wall         is produced from at least one of the following materials:     -   i) high-grade steel;     -   ii) aluminium;     -   iii) copper;     -   iv) titanium;     -   v) an austenitic high-grade steel;     -   vi) a high-grade steel of type 316 (according to AISI).

These materials have proved to be particularly advantageous. For example, by means of aluminium, a very lightweight configuration of the channel, of the wall and/or of the cooling conduit can be achieved. High-grade steel has proved advantageous particularly in the food industry, since, here, a surface of the channel and/or of the cooling conduit is obtained which does not usually lead to reactions with the articles to be frozen and which can easily be cleaned. What is in this case preferred is a design composed of high-grade steel of type 316 according to AISI (American Iron and Steel Institute) which comprises austenitic chrome-nickel steels with an alloy fraction of molybdenum. An austenitic high-grade steel is understood to mean a high-grade steel which contains up to 0.15% by weight of carbon, at least 16% by weight of chrome and nickel and/or manganese as alloying elements.

According to a further advantageous refinement of the device according to the invention, the channel has, at least in part-regions, an open cross section.

This is understood, in particular, to mean that the channel, in these part-regions, is freely accessible in mechanical terms, for example by or with a brush or the like. This advantageously allows a mechanical cleaning of the channel which is advantageous particularly in the case of a change of the articles to be frozen.

According to a further advantageous refinement of the device according to the invention, the cooling conduit has an essentially closed, in particular completely closed cross section. This minimizes the loss of second coolant due to evaporation and permits the thermal insulation of regions of the cooling conduit which do not face the channel.

According to a further advantageous refinement of the device according to the invention, the channel is designed with an inclination to a horizontal. Preferably, here, the inclination lies in a range of 6 millimetres per litre or less, in particular in the range of 3 millimetres per metre or less.

According to a further advantageous refinement, the means for introducing the articles, which means comprise, for example, a drop dispenser for dropping the liquid and/or pasty mass into the first stream, are formed at or adjacently to a first longitudinal end of the channel. This makes it possible to utilize essentially the entire channel or the entire channels over the full length for cooling or freezing the articles. Furthermore, preferably, means for separating the articles from the first coolant stream are formed, in particular, at or adjacently to a second longitudinal end of the channel, the second longitudinal end being formed opposite to the first longitudinal end. The means for separating the articles from the first coolant stream may, for example, be a screen or the like.

According to a further advantageous refinement, the channel is connected to a sump such that the first stream of a first coolant can flow out of the channel into the sump.

The sump thus serves for collecting the first coolant, preferably nitrogen.

According to a further advantageous refinement of the device, the cooling conduit can be connected to the sump such that the second stream of a second coolant, after flowing through the cooling conduit, flows into the sump.

Thus, advantageously, the second stream of the second coolant can be utilized for feeding the first stream of the first coolant, without contaminations of the cooling conduit being able to occur. Preferably, this may take place in that possible evaporation losses of the first coolant are compensated.

Furthermore, it is advantageous that the first coolant conveyance unit comprises at least one Archimedean screw.

Archimedean screws have proved advantageous for the transport and raising of, in particular, liquid gases, such as, for example, liquid nitrogen or liquid helium. In particular, the Archimedean screw is designed such that it can convey a first coolant out of the coolant sump and thus assists or fully maintains the first stream of the first coolant.

The second coolant conveyance unit preferably comprises a coolant source.

A coolant source is understood here to mean a supply unit which makes available essentially pure, preferably completely pure second coolant, in particular with less than 0.1% by weight of impurities. This is preferably pure liquid nitrogen. The coolant source may comprise a line system and/or a coolant reservoir.

It is particularly preferred, in this context, that the coolant source is suitable for ensuring a pressure of the second coolant in the cooling conduit such that the second coolant can flow through the cooling conduit by virtue of this pressure.

In particular, the coolant source comprises a reservoir of the second coolant and/or conveyance means, such as, for example, at least one pump.

According to a further advantageous refinement of the device according to the invention, pressure compensation means are formed in at least one of the following components:

a) the coolant source and b) the delivery line, which ensure a uniform pressure of the second coolant in the cooling conduit independently of a pressure of the second coolant upstream of the pressure compensation means. The pressure compensation means serves, in particular, as a buffer, by means of which pressure fluctuations upstream of the pressure compensation means are damped. A uniform pressure of the second coolant is preferably understood to mean that, during uniform operation, fluctuations of at most +/−5% around an average pressure occur downstream of the pressure compensation means.

Thus, temporary pressure pulses can be damped away, which would otherwise lead to a non-uniform cooling power in the cooling conduit. A refinement is in this case preferred in which the pressure compensation means comprise pressure compensation based on a rolling diaphragm.

The details and advantages explained with regard to the method according to the invention can be transferred and applied equally to the device according to the invention, and vice versa. The invention will be explained in more detail below with reference to the accompanying drawing in which, diagrammatically,

FIG. 1 shows an exemplary embodiment of a device according to the invention;

FIG. 2 shows a first detail of the exemplary embodiment;

FIG. 3 shows a second detail of the exemplary embodiment;

FIG. 4 shows a further exemplary embodiment of a device according to the invention in a first state;

FIG. 5 shows a detail of the further exemplary embodiment in a second state; and

FIG. 6 shows an exemplary embodiment in which a plurality of channels have a common cooling conduit.

FIG. 1 shows a basic diagram of a device 1 according to the invention for the cooling of articles 5 in longitudinal section. The device 1 comprises at least one channel 2 which can be connected to a first coolant source 3 such that a first stream 4 of a first coolant can flow through the channel 2. In the present exemplary embodiment, the articles 5 to be cooled are drops of a pasty or liquid mass to be frozen which are introduced into the first stream 4 by means for introducing the articles 5, the said means comprising a drop former 6, so that the channel 2 has flowing through it a first stream 4 of a first coolant, into which stream the articles 5 to be cooled are introduced and with which these are co-moved. Owing to thermal contact of the articles 5 with the coolant in the first stream 4, the articles 5 cool down. At the same time, the first coolant heats up. When liquid nitrogen is used as the first coolant, an at least partial evaporation of the nitrogen may occur.

The degree of the temperature of the articles 5 which is reached after these flow through the channel 2 is in this case dependent on the dwell time in the channel 2 and on the temperature of the first coolant. The first coolant used is preferably liquid nitrogen. The channel 2 itself is described below in detail with reference to exemplary embodiments.

The first coolant source 3 comprises an Archimedean screw, by means of which liquid nitrogen can be conveyed out of a nitrogen sump 7. Articles 5 in the first stream 4 move, together with this, through the channel 2. After reaching the channel end 8, the first stream 4 is transferred, together with articles 5, onto the separation delivery 9 which leads the mixture of the first stream 4 and of articles 5 to the product separator 10. The product separator 10 is part of a second Archimedean screw 11. A mixture 12 of articles 5 and of cold gas, which has occurred due to the at least partial evaporation of the liquid nitrogen, is led through this second Archimedean screw 11. The product separator 10 in this case forms an externally perforated region of the second Archimedean screw 11, through which region, owing to the centrifugal force which takes effect and because of the gravitational force which takes effect, the liquid nitrogen flows as the first coolant out of the second Archimedean screw 11 and as a liquid nitrogen stream 13 into the nitrogen sump 7. At the end of the second Archimedean screw 11, a discharge of a product stream 14 takes place, which contains the articles 5 cooled according to the invention, in particular at least superficially frozen drops of a pasty or liquid mass, for example of an edible and/or consumable mass, and a discharge of a cold-gas stream 15 takes place. The product stream 14 is extracted through the product outlet 16. The entire device 1 is formed in an essentially gas-tight housing which prevents the escape of evaporated liquid nitrogen and which constitutes thermal insulation for reducing the coolant consumption. Furthermore, the device 1 for the cooling of articles 5 has a second coolant conveyance unit 23. The second coolant conveyance unit 23 comprises a delivery line 24, by means of which second coolant 25 can be conducted into the cooling conduit. For this purpose, the delivery line 24 is connected to a supply system, not shown in any more detail, for the second coolant 25, for example liquid nitrogen. This may, in particular, be a tank system which, if appropriate, is also connected to a corresponding conveyance unit having a pump. After flowing through the cooling conduit 20, the second coolant 25 leaves the cooling conduit 20 through the discharge line 26. The tie-up of the delivery line 24 to the cooling conduit 20 is shown in detail in FIG. 3 by way of example. The tie-up of the discharge line 26 to the cooling conduit 20 is shown by way of example in FIG. 2.

According to the invention, therefore, during operation, the first stream of the first coolant flows through the channel together with the articles 5 to be cooled, while the second stream 21 of the second coolant 25 flows through the cooling conduit 20. In this case, the first stream 4 is fed from a first coolant conveyance unit 3 and the second stream 21 is fed from a second coolant conveyance unit 23. The method according to the invention and the device 1 according to the invention have the advantage that the second stream 21 of the second coolant can be selected such that it conforms to the highest possible hygiene and cleanliness standards. For example, the second coolant selected may be pure liquid nitrogen. Since this second stream of nitrogen does not come into contact with the articles 5 to be frozen, this second stream 21 is also not contaminated. The result of this is that, in comparison with systems known from the prior art, in which the same coolant flows through the cooling conduit 20 as flows through the channel, the cooling conduit 20 is contaminated to a markedly greater extent and may become blocked. These blockages in the cooling conduit can be broken down only with great difficulty in systems known from the prior art, since access is usually not afforded. This necessitates a time-intensive use of, for example, chemical cleaning agents which cause high standstill times for the corresponding devices. Consequently, the device according to the invention and the method according to the invention have the advantage that there are here longer operating times and shorter maintenance times of the device, and that hygiene regulations can be adhered to much more easily. The latter is of major importance particularly in the cooling or freezing of foods.

FIG. 2 shows diagrammatically the second tie-up region 28 in detail. It can be seen how the second stream 21 of the second coolant 25 flows through the cooling conduit 20 in order then to be steered in the deflection region 29 into the discharge line 26. In this exemplary embodiment, the cooling conduit 20 is formed on an underside 19 of a wall 22, while the channel 2 is formed on the top side 18 of the wall 22. The first stream 4 of a first coolant flows through the channel 2 together with the articles 5 to be frozen, not shown here.

FIG. 3 shows an exemplary embodiment of the first tie-up region 27 diagrammatically in detail. The delivery line 24, designed as a metal fabric hose, is connected to the cooling conduit 20 in the vicinity of the channel end 8. The second coolant 25 flows through the delivery line 24 into the cooling conduit 20 and thus cools the channel 2 from below. The first stream 4 of a first coolant flows through the channel 2 together with the articles 5 to be cooled, not shown here. After reaching the channel end, which is designed in the form of a funnel 30, the first stream 4 is led through the separation delivery 9 to the product separator 10.

FIG. 4 shows a detail of a further exemplary embodiment of a device 1 according to the invention for the cooling of articles 5. In this case, a coolant source 31, which comprises a coolant reservoir 32 and a conveying means 33, such as a pump, is connected to the delivery line 24. Furthermore, corresponding valves 34 regulating the throughflow of the coolant are designed with corresponding pressure gauges 35. The second coolant conveyance unit 23 may alternatively also be designed without conveying means, valves 34 and/or pressure gauges 35. Furthermore, the second coolant conveyance unit comprises optional pressure compensation means 36. These comprise a rolling diaphragm 37 which is moveable with respect to an adjustable actuating member 38. By the actuating member 38 being adjusted, the force on the rolling diaphragm 37 and consequently the prevailing pressure, around which compensation needs to take place, can be set. In the case of low prevailing pressures, the rolling diaphragm 37 has, for example, a position according to FIG. 4, while, at higher pressures, there may be a position according to FIG. 5. The actuating member 38 may, for example, be designed to be adjustable by means of a screw and to operate counter to a fly spring.

The pressure compensation means 36 may be formed independently of the exact design of the channel 2 and of the exact designs of the cooling conduit 20 and/or of the channel 2.

FIG. 6 shows diagrammatically an embodiment of a plurality of channels 2 which have a common cooling conduit 20. The channels 2 are in this case formed by a wall 22. This wall is produced from metal, in particular from high-grade steel, preferably from high-grade steel of type 316 according to AISI. In order to prevent deformations of this wall 22, cross-sectional stabilizers 39 are formed. The cooling conduit 20 is formed from a basic component 40 which is connected to the wall 22 at a connection region 41. Other forms of the channel 2 are possible and according to the invention.

The method according to the invention and the device 1 according to the invention for the cooling of articles 5 allow a simple and effective cooling, in particular an at least partial freezing of the articles 5, in that a second stream 21 of a second coolant 25 can flow through a cooling conduit 20 which is designed such that a cooling of a channel 2, through which a first stream 4 of a first coolant, which carries the corresponding articles 5 with it, can flow, can take place. The second stream 21 of a second coolant 25 is advantageously a high-purity coolant stream which, in particular, comprises essentially pure nitrogen. High purity is in this context understood to mean, in particular, that the second stream 21 of the second coolant 25 carries with it no articles 5 or remains of articles 5 or other impurities. As a result, the cooling conduit 20 remains clean and does not have to be cleaned in a complicated way. Preferably, after flowing through the cooling conduit 20, the second stream 21 of the second coolant 25 is combined with the first stream 4 of the first coolant, for example in that the second stream 21 of the coolant 25 is introduced into the sump 7.

LIST OF REFERENCE SYMBOLS

-   1 Device for the cooling of articles -   2 Channel -   3 First coolant conveyance unit -   4 First stream -   5 Article -   6 Drop former -   7 Nitrogen sump -   8 Channel end -   9 Separation delivery -   10 Product separator -   11 Second Archimedean screw -   12 Mixture -   13 Liquid nitrogen stream -   14 Product stream -   15 Cold-gas stream -   16 Product outlet -   17 Housing -   18 Top side -   19 Underside -   20 Cooling conduit -   21 Second stream -   22 Wall -   23 Second coolant conveyance unit -   24 Delivery line -   25 Second coolant -   26 Discharge line -   27 First tie-up region -   28 Second tie-up region -   29 Deflection region -   30 Funnel -   31 Coolant source -   32 Coolant reservoir -   33 Conveying means -   34 Valve -   35 Pressure gauge -   36 Pressure compensation means -   37 Rolling diaphragm -   38 Actuating member -   39 Cross-sectional stabilizer -   40 Basic component -   41 Connection region 

1-17. (canceled)
 18. A method for the cooling of articles, the method comprising the steps of: flowing a first stream of a first coolant from a first coolant conveyance unit through at least one channel; introducing the articles into the at least one channel; feeding a second stream of a second coolant from a second coolant conveyance unit; and cooling the at least one channel by the second stream of the second coolant.
 19. The method of claim 18, further comprising the steps of: separating the first stream of the first coolant from the articles after flowing through the at least one channel; and collecting the first coolant in a sump.
 20. The method of claim 19, wherein the first coolant conveyance unit comprises the sump.
 21. The method of claim 19, further comprising the step of delivering the second coolant to the sump after cooling the at least one channel.
 22. The method of claim 18, wherein the direction of the first stream and that of the second stream are essentially opposite to one another.
 23. The method of claim 18, wherein the second stream flows beneath the at least one channel.
 24. The method of claim 18, wherein the cooling step further comprises feeding the second stream of the second coolant into a cooling conduit at a pressure such that the second stream can flow through the cooling conduit by virtue of this pressure.
 25. A device for the cooling of articles, comprising: at least one channel connectable to a first coolant conveyance unit such that a first stream of a first coolant flows through the at least one channel and having a cooling conduit connectable to a second coolant conveyance unit such that a second stream of a second coolant flows through the cooling conduit; and a drop dispenser for introducing the articles into the first stream being formed.
 26. The device of claim 25, wherein the at least one channel is at least partially delimited by at least one wall, the cooling conduit being formed on a side lying opposite the channel.
 27. The device of claim 25, wherein at least one of the following components: a) the at least one channel; b) the at least one wall; and c) the cooling conduit are produced from at least one of the following materials: i) high-grade steel; ii) aluminum; iii) copper; iv) titanium; v) an austenitic high-grade steel; and vi) an austenitic high-grade steel of type 316 (according to AISI).
 28. The device of claim 25, wherein at least part of the channel has an open cross section.
 29. The device of claim 25, wherein at least part of the cooling conduit has a closed cross section.
 30. The device of claim 25, further comprising a sump connected to the channel such that the first stream of the first coolant flows out of the channel into the sump.
 31. The device of claim 30, further comprising connecting the cooling conduit to the sump such that the second stream of the second coolant, after flowing through the cooling conduit, flows into the sump.
 32. The device of claim 25, wherein the second coolant conveyance unit comprises a coolant source.
 33. The device of claim 32, wherein the coolant source is suitable for ensuring a pressure of the second coolant in the cooling conduit such that the second coolant can flow through the cooling conduit by virtue of this pressure.
 34. The device of claim 25, further comprising a rolling diaphragm with adjustable actuating member formed in at least one of the following components: a) a coolant source and b) a delivery line, which ensure a uniform pressure of the second coolant in the cooling conduit independently of a pressure of the second coolant upstream of the pressure compensation means. 